PROJECT SUMMARY/ABSTRACT The objective of this postdoctoral fellowship (F32) application is to promote the Candidate, Maura Kepper, Ph.D., into a path of independent research focused on identifying targets and translating findings to intervention strategies that alter neighborhood environments to promote the healthy development of our youth. The proposed research will employ a convergent mixed methods approach to generate a comprehensive understanding of how and which environmental factors play a crucial role in parental constraint of outdoor play and contribute to low levels of within-neighborhood physical activity. Given the Candidate's significant research experience exploring the influence of neighborhood environments on health, the goal of this proposal is to integrate her current quantitative skills with focused training in new learning areas to provide a strong foundation for an independent research career. Together, the sponsor, co-sponsors and consultants are fully committed to assisting the Candidate to reach her research training and career development goals and to successfully implement the proposed research. The proposed study provides the opportunity for the necessary training in 1) the management, analysis, and interpretation of linked accelerometry data, global positioning systems (GPS) technologies, and spatial data (e.g. neighborhood boundaries, locations of parks) and 2) mixed methods research. The Candidate will benefit from the proposed project by collaborating as an investigator on a large longitudinal, observational study, Translational Investigation of Growth and Everyday Routines in Kids (TIGER Kids) Study (USDA 3092-51000-056-04A), that will expand her research to a large cohort (n=340) of African American and Caucasian girls and boys, 10 to 16 years of age. The proposed research will add state- of-the-art quantitative measures (i.e., GPS, accelerometry, and virtual Systematic Social Observation) and in- depth interviews with parents/guardians of TIGER Kids participants to gain a comprehensive understanding of how neighborhood social and physical environments influence parental constraint of outdoor play and reduce offspring's within-neighborhood physical activity. This research proposal has two main aims: A1) implement quantitative methods to delineate the relationships between the social environment (parental perceived collective efficacy), parental constrained outdoor play practices and offspring within-neighborhood physical activity and A2) implement qualitative methods (in-depth interviews) among parents/guardians living in varied neighborhood physical environments (i.e., low vs. high incivilities) to gain in-depth information and perspectives of the social environment's influence on constrained outdoor play practices. The proposal also aims to quantitatively examine the potential moderating effect of the neighborhood physical environment (i.e., incivilities) (A1a). Findings from the proposed study will provide a critical foundation for the Candidate's independent research to develop community-based interventions to reduce parental constraints on outdoor play and increase physical activity levels that promote healthy development during childhood and adolescence.